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Abstract: Abstract Around 60% of useful energy is wasted in industry, homes, or transportation. Therefore, there has been increasing attention on thermoelectric materials for their ability to harvest waste heat into useful energy. The efficiency of a thermoelectric material depends on its electrical conductivity, Seebeck coefficient, and thermal conductivity in a conflicting manner which results in efficiency optimization challenges. Single crystals and polycrystalline layered materials have comparatively better thermoelectric and mechanical properties in a certain direction. Texture engineering is a special strategy that allows the exploitation of superior material properties in a specific direction. Texturing could be achieved by various sintering and deformation methods, which yield defects improving thermoelectric and mechanical properties. The results show that for (Bi,Sb)2Te3, Bi2(Se,Te)3, CuSbSe2, and SnSe, significant enhancement in the thermoelectric figure of merit is achieved by enhancing the preferred orientation. Texture engineering provides a wide range of strategies to elevate the zT of anisotropic materials to values comparable to those of their single crystalline counterparts. PubDate: 2023-02-06
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Abstract: Abstract A sol–gel tandem with a solid-phase modification procedure was developed to synthesize Li2TiO3-doped LiCoO2 together with phosphate coatings (denoted as LCO-Ti/P), which possesses excellent high-voltage performance in the range of 3.0–4.6 V. The characterizations of X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy illustrated that the modified sample LCO-Ti/P had the dopant of monoclinic Li2TiO3 and amorphous Li3PO4 coating layers. LCO-Ti/P has an initial discharge capacity of 211.6 mAh/g at 0.1 C and a retention of 85.7% after 100 cycles at 1 C and 25 ± 1 °C between 3.0 and 4.6 V. Nyquist plots reflect that the charge transfer resistance of LCO-Ti/P after 100 cycles at 1 C is much lower than that of the spent LCO, which benefits Li-ion diffusion. Density functional theory calculations disclose the superior lattice-matching property of major crystal planes for Li2TiO3 and LiCoO2, the lower energy barriers for Li-ion diffusion in Li2TiO3, and the suppressed oxygen release performance resulting from phosphate adsorption. This work provides useful guidance on the rational design of the high-voltage performance of modified LiCoO2 materials in terms of lattice-matching properties aside from the phosphate coating to reduce the energy barriers of Li-ion diffusion and enhance cycling stability. PubDate: 2023-02-01
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Abstract: Abstract A three-dimensional multicomponent multiphase lattice Boltzmann model (LBM) is established to model the coupled two-phase and reactive transport phenomena in the cathode electrode of proton exchange membrane fuel cells. The gas diffusion layer (GDL) and microporous layer (MPL) are stochastically reconstructed with the inside dynamic distribution of oxygen and liquid water resolved, and the catalyst layer is simplified as a superthin layer to address the electrochemical reaction, which provides a clear description of the flooding effect on mass transport and performance. Different kinds of electrodes are reconstructed to determine the optimum porosity and structure design of the GDL and MPL by comparing the transport resistance and performance under the flooding condition. The simulation results show that gradient porosity GDL helps to increase the reactive area and average concentration under flooding. The presence of the MPL ensures the oxygen transport space and reaction area because liquid water cannot transport through micropores. Moreover, the MPL helps in the uniform distribution of oxygen for an efficient in-plane transport capacity. Crack and perforation structures can accelerate the water transport in the assembly. The systematic perforation design yields the best performance under flooding by separating the transport of liquid water and oxygen. PubDate: 2023-02-01
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Abstract: Abstract Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. Additionally, despite the higher electrochemical performance observed, the cell with a counter-flow arrangement featured by a larger hot area and higher maximum temperature gradients is not preferable for a ceramic SOFC system considering thermal durability. Overall, this study could provide insightful thermal information for the operating condition selection, structure design, and stability assessment of realistic SOFCs combined with their internal reforming process. PubDate: 2023-02-01
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Abstract: Abstract Over the past half-century, plastic consumption has grown rapidly due to its versatility, low cost, and unrivaled functional properties. Among the different implemented strategies for recycling waste plastics, pyrolysis is deemed the most economical option. Currently, the wax obtained from the pyrolysis of waste plastics is mainly used as a feedstock to manufacture chemicals and fuels or added to asphalt for pavement construction, with no other applications of wax being reported. Herein, the thermal pyrolysis of three common waste polyolefin plastics: high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), was conducted at 450 °C. The waste plastics-derived waxes were characterized and studied for a potential new application: phase change materials (PCMs) for thermal energy storage (TES). Gas chromatography–mass spectrometry analysis showed that paraffin makes up most of the composition of HDPE and LDPE waxes, whereas PP wax contains a mixture of naphthene, isoparaffin, olefin, and paraffin. Differential scanning calorimetry (DSC) analysis indicated that HDPE and LDPE waxes have a peak melting temperature of 33.8 °C and 40.3 °C, with a relatively high latent heat of 103.2 J/g and 88.3 J/g, respectively, whereas the PP wax was found to have almost negligible latent heat. Fourier transform infrared spectroscopy and DSC results revealed good chemical and thermal stability of HDPE and LDPE waxes after 100 cycles of thermal cycling. Performance evaluation of the waxes was also conducted using a thermal storage pad to understand their thermoregulation characteristics for TES applications. PubDate: 2022-12-21
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Abstract: Abstract Designing high-performance nanostructured electrode materials is the current core of electrochemical energy storage devices. Multi-scaled nanomaterials have triggered considerable interest because they effectively combine a library of advantages of each component on different scales for energy storage. However, serious aggregation, structural degradation, and even poor stability of nanomaterials are well-known issues during electrochemically driven volume expansion/contraction processes. The confinement strategy provides a new route to construct controllable internal void spaces to avoid the intrinsic volume effects of nanomaterials during the reaction or charge/discharge process. Herein, we discuss the confinement strategies and methods for energy storage-related electrode materials with a one-dimensional channel, two-dimensional interlayer, and three-dimensional space as reaction environments. For each confinement environment, the correlation between the confinement condition/structure and the behavioral characteristics of energy storage devices in the scope of metal–ion batteries (e.g., Li-ion, Na-ion, K-ion, and Mg-ion batteries), Li–S batteries (LSBs), Zn–air batteries (ZIBs), and supercapacitors. Finally, we discussed the challenges and perspectives on future nanomaterial confinement strategies for electrochemical energy storage devices. PubDate: 2022-12-15
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Abstract: Abstract The development of reliable and low-cost energy storage systems is of considerable value in using renewable and clean energy sources, and exploring advanced electrodes with high reversible capacity, excellent rate performance, and long cycling life for Li/Na/Zn-ion batteries and supercapacitors is the key problem. Particularly because of their diverse structure, high specific surface area, and adjustable redox activity, electrically conductive metal–organic frameworks (c-MOFs) are considered promising candidates for these electrochemical applications, and a detailed overview of the recent progress of c-MOFs for electrochemical energy storage and their intrinsic energy storage mechanism helps realize a comprehensive and systematic understanding of this progress and further achieve highly efficient energy storage and conversion. Herein, the chemical structure of c-MOFs and their conductive mechanism are first introduced. Subsequently, a comprehensive summarization of the current applications of c-MOFs in energy storage systems, namely supercapacitors, LIBs, SIBs, and ZIBs, is presented. Finally, the prospects and challenges of c-MOFs toward much higher-performance energy storage devices are presented, which should illuminate the future scientific research and practical applications of c-MOFs in energy storage fields. PubDate: 2022-12-09
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Abstract: Abstract Renewable and economical generation of hydrogen via electrochemical methods shows great potential in addressing the energy crisis. In this study, an emerging molten salt method was adopted for the synthesis of a cerium-modified rhenium disulfide nanosheet for electrical hydrogen evolution reactions. The prepared 1% Ce-doped rhenium disulfide (ReS2) sample showed promoted hydrogen evolution performance in both acid and alkaline electrolytes compared to bare ReS2. Generating of abundant defects in ReS2 exposed more reaction active sites. Moreover, adding cerium accelerated the hydrogen evolution dynamics. Hopefully, this work will offer new insight into developing ReS2-based electrocatalysts for hydrogen evolution reactions. PubDate: 2022-12-01
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Abstract: Silicon (Si) is a potential high-capacity anode material for the next-generation lithium-ion battery with high energy density. However, Si anodes suffer from severe interfacial chemistry issues, such as side reactions at the electrode/electrolyte interface, leading to poor electrochemical cycling stability. Herein, we demonstrate the fabrication of a conformal fluorine-containing carbon (FC) layer on Si particles (Si-FC) and its in situ electrochemical conversion into a LiF-rich carbon layer above 1.5 V (vs. Li+/Li). The as-formed LiF-rich carbon layer not only isolates the active Si and electrolytes, leading to the suppression of side reactions, but also induces the formation of a robust solid–electrolyte interface (SEI), leading to the stable interfacial chemistry of as-designed Si-FC particles. The Si-FC electrode has a high initial Coulombic efficiency (CE) of 84.8% and a high reversible capacity of 1450 mAh/g at 0.4 C (1000 mA/g) for 300 cycles. In addition, a hybrid electrode consisting of 85 wt% graphite and 15 wt% Si-FC, and mass 2.3 mg/cm2 loading delivers a high areal capacity of 2.0 mAh/cm2 and a high-capacity retention of 93.2% after 100 cycles, showing the prospects for practical use. Graphical PubDate: 2022-11-30
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Abstract: Abstract The safe operating voltage and low volume variation of Li3VO4 (LVO) make it an ideal anode material for lithium (Li)-ion batteries. However, the insufficient understanding of the inner storage mechanism hinders the design of LVO-based electrodes. Herein, we investigate, for the first time, the Li-ion storage activity in LVO via Cl doping. Moreover, N-doped C coating was simultaneously achieved in the Cl doping process, resulting in synergistically improved reaction kinetics. As a result, the as-prepared Cl-doped Li3VO4 coated with N-doped C (Cl-LVO@NC) electrodes deliver a discharge capacity of 884.1 mAh/g after 200 cycles at 0.2 A/g, which is the highest among all of the LVO-based electrodes. The Cl-LVO@NC electrodes also exhibit high-capacity retention of 331.1 mAh/g at 8.0 A/g and full capacity recovery after 5 periods of rate testing over 400 cycles. After 5000 cycles at 4.0 A/g, the discharge capacity can be maintained at 423.2 mAh/g, which is superior to most LVO-based electrodes. The Li-ion storage activity in LVO via Cl doping and significant improvement in the high-rate Li-ion storage reported in this work can be used as references for the design of advanced LVO-based electrodes for high-power applications. PubDate: 2022-11-28
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Abstract: Abstract Conversion of carbon dioxide (CO2) into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization. Although various types of semiconductor materials have been intensively explored, some severe issues, such as rapid charge recombination and sluggish redox reaction kinetics, remain. In this regard, cocatalyst modification by trapping charges and boosting surface reactions is one of the most efficient strategies to improve the efficiency of semiconductor photocatalysts. This review focuses on recent advances in CO2 photoreduction over cost-effective and earth-abundant cobalt (Co)-based cocatalysts, which are competitive candidates of noble metals for practical applications. First, the functions of Co-based cocatalysts for promoting photocatalytic CO2 reduction are briefly discussed. Then, different kinds of Co-based cocatalysts, including cobalt oxides and hydroxides, cobalt nitrides and phosphides, cobalt sulfides and selenides, Co single-atom, and Co-based metal–organic frameworks (MOFs), are summarized. The underlying mechanisms of these Co-based cocatalysts for facilitating CO2 adsorption–activation, boosting charge separation, and modulating intermediate formation are discussed in detail based on experimental characterizations and density functional theory calculations. In addition, the suppression of the competing hydrogen evolution reaction using Co-based cocatalysts to promote the product selectivity of CO2 reduction is highlighted in some selected examples. Finally, the challenges and future perspectives on constructing more efficient Co-based cocatalysts for practical applications are proposed. PubDate: 2022-11-28
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Abstract: Solid-state batteries (SSBs) have been considered the most promising technology because of their superior energy density and safety. Among all the solid-state electrolytes (SEs), Li7La3Zr2O12 (LLZO) with high ionic conductivity (3 × 10−4 S/cm) has been widely investigated. However, its large-scale production in ambient air faces a challenge. After air exposure, the generated Li2CO3 layer deteriorates the ionic conductivity and interfacial wettability, thus greatly compromising the electrochemical performance of SSBs. Many works aim to eliminate this layer to recover the pristine LLZO surface. Unfortunately, few articles have emphasized the merits of Li2CO3. In this review, we focus on the two-sidedness of Li2CO3. We discuss the various characteristics of Li2CO3 that can be used and recapitulate the strategies that utilize Li2CO3. Insulating Li2CO3 is no longer an obstacle but an opportunity for realizing intimate interfacial contact, high air stability, and outstanding electrochemical performance. This review aims to offer insightful guidelines for treating air-induced Li2CO3 and lead to developing the enhanced air stability and electrochemical performance of LLZO. Graphical PubDate: 2022-11-27
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Abstract: Abstract C–O bonds are widely found in pharmaceuticals and natural products and have various pharmacological activities. Therefore, developing effective strategies for constructing compounds containing C–O bonds has become a research hotspot among chemists. Organic electrochemical synthesis is a green, mild, and efficient strategy that shows great potential in the synthesis of compounds containing C–O bonds. This review introduces the reactions of compounds containing C–O bonds recently constructed by electrochemical methods and expounds the corresponding reaction mechanism to provide a reference for applying such reactions in organic synthesis. PubDate: 2022-11-23
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Abstract: Abstract Novel graphene-like boron nitride (BN)/Bi3O4Br photocatalysts have been controllably synthesized through a facile solvothermal method for the first time. Layer contact stacking between graphene-like BN and ultrathin Bi3O4Br was achieved with strong interaction. Dehalogenation is designed to harvest more visible light, and the ultrathin structure of Bi3O4Br is designed to accelerate charge transfer from inside to the surface. After graphene-like BN was engineered, photocatalytic performance greatly improved under visible light irradiation. Graphene-like BN can act as a surface electron-withdrawing center and adsorption center, facilitating molecular oxygen activation. O2•− was determined to be the main active species during the degradation process through analyses of electron spin resonance and XPS valence band spectra. PubDate: 2022-11-16
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Abstract: Abstract Computational models that ensure accurate and fast responses to the variations in operating conditions, such as the cell temperature and relative humidity (RH), are essential monitoring tools for the real-time control of proton exchange membrane (PEM) fuel cells. To this end, fast cell-area-averaged numerical simulations are developed and verified against the present experiments under various RH levels. The present simulations and measurements are found to agree well based on the cell voltage (polarization curve) and power density under variable RH conditions (RH = 40%, RH = 70%, and RH = 100%), which verifies the model accuracy in predicting PEM fuel cell performance. In addition, computationally feasible reduced-order models are found to deliver a fast output dataset to evaluate the charge/heat/mass transfer phenomena as well as water production and two-phase flow transport. Such fast and accurate evaluations of the overall fuel cell operation can be used to inform the real-time control systems that allow for the improved optimization of PEM fuel cell performance. PubDate: 2022-11-04
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Abstract: Abstract Tin (Sn)-based perovskite solar cells (PSCs) have received increasing attention in the domain of photovoltaics due to their environmentally friendly nature. In this paper, numerical modeling and simulation of hole transport material (HTM)-free PSC based on methyl ammonium tin triiodide (CH3NH3SnI3) was performed using a one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The effect of perovskite thickness, interface defect density, temperature, and electron transport material (ETM) on the photovoltaic performance of the device was explored. Prior to optimization, the device demonstrated a power conversion efficiency (PCE) of 8.35%, fill factor (FF) of 51.93%, short-circuit current density (Jsc) of 26.36 mA/cm2, and open circuit voltage (Voc) of 0.610 V. Changing the above parameters individually while keeping others constant, the obtained optimal absorber thickness was 1.0 μm, the interface defect density was 1010 cm–2, the temperature was 290 K, and the TiO2 thickness was 0.01 μm. On simulating with the optimized data, the final device gave a PCE of 11.03%, FF of 50.78%, Jsc of 29.93 mA/cm2, and Voc of 0.726 V. Comparing the optimized and unoptimized metric parameters, an improvement of ~ 32.10% in PCE, ~ 13.41% in Jsc, and ~ 19.02% in Voc were obtained. Therefore, the results of this study are encouraging and can pave the path for developing highly efficient PSCs that are cost-effective, eco-friendly, and comparable to state-of-the-art. PubDate: 2022-10-17
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Abstract: Abstract The ubiquity of N-heterocycles in marketed drugs makes the development of metal-free methodologies for constructing C–N bonds of considerable importance. As an environmentally friendly method, electro-oxidative intramolecular C–H amination has emerged as a powerful platform for synthesizing nitrogen-containing heterocycles under metal- and external oxidant-free conditions. In this minireview, the main achievements in this direction since 2020 are summarized, with an emphasis on the substrate scope and mechanistic aspects. The reactions are classified into two categories: direct and indirect electro-oxidative intramolecular C–H aminations. PubDate: 2022-10-16
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Abstract: Abstract Perovskite solar cells (PSCs) have undergone a dramatic increase in laboratory-scale efficiency to more than 25%, which is comparable to Si-based single-junction solar cell efficiency. However, the efficiency of PSCs drops from laboratory-scale to large-scale perovskite solar modules (PSMs) because of the poor quality of perovskite films, and the increased resistance of large-area PSMs obstructs practical PSC applications. An in-depth understanding of the fabricating processes is vital for precisely controlling the quality of large-area perovskite films, and a suitable structural design for PSMs plays an important role in minimizing energy loss. In this review, we discuss several solution-based deposition techniques for large-area perovskite films and the effects of operating conditions on the films. Furthermore, different structural designs for PSMs are presented, including the processing technologies and device architectures. PubDate: 2022-10-02
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Abstract: Abstract The synthesis of aryl iodides from commercially available raw chemicals by simple, cheap and green strategies is of fundamental significance. Aryl iodides can undergo a series of homo-/cross-coupling reactions for the synthesis of important industrial chemicals and materials. Traditional methods require the electrophilic substitution on aromatic compounds by iodine or hypervalent iodine compounds, which suffers from the use of erosive halogens or hazardous oxidants. With the development of green chemistry in the field of electrochemical synthesis, anodic oxidation-derived I+ cations have been used for substitution reactions. However, the selectivity of the iodination by these electrochemical methods remains unsatisfactory. We believed that the anolyte is contaminated by trace platinum species from the working electrode. Herein, we report the generation of active I+ species from the anodic oxidation of I2 in acetonitrile using a glassy carbon electrode. With the presence of H+, electrolyte prepared with a glassy carbon anode can react with anisole to selectively form 4-iodoanisole with a yield as high as 97%. On contrast, the electrolytes prepared from Pt and graphite anodes finished the reaction with yields of 16% and 60% for 4-iodoanisole, respectively. This electrochemical method also applies to the iodination of toluene, benzonitrile and bromobenzene, delivering the target para-iodination products with 92%, 84%, and 73% yields, respectively. Thus, an atom-efficient and highly selective aryl iodination method was developed without the use of excessive oxidants. PubDate: 2022-09-07
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Abstract: Abstract Metal–organic frameworks (MOFs), which are generally considered to be crystalline materials comprising metal centers and organic ligands, have attracted growing attention because of their controllable structures and high porosity. MOFs based on transition metals (Fe, Co, Ni) are highly efficient electrode materials for electrochemical energy storage. In this review, the characteristics of Fe-MOFs, Co-MOFs, Ni-MOFs, and their derivatives are summarized, and the relationships between the structures and performance are unveiled in depth. Additionally, their applications in lithium–ion batteries, lithium–sulfur batteries, and supercapacitors are discussed. This review sheds light on the development of MOFs and their derivatives to realize excellent electrochemical performance. PubDate: 2022-09-04
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